Artificial heart pump or assist

ABSTRACT

An implantable artificial heart pump or heart assist for providing or enhancing a controlled cyclic blood flow through an artery, the pump including a tubular section secured between adjacent ends of a severed artery forming a continuous blood flow passage, and having a plurality of axially spaced but adjacent sleeves encircling this section. The sleeves are sequentially constricted about the tubular section to provide alternately pumping and suction upon the blood flowing through the section, the sleeves being energized by high and low pressure working fluid from an external or implantable power source. Where the power source is an implantable Stirling engine, pressure variations are available from the gas working space, or from an oil pump in the crankcase, or from a compressor driven by the engine.

United States Patent [1 1 Pedroso [451 May27, 1975 [73] Assignee: NorthAmerican Philips Corporation, New York, NY.

[22] Filed: Mar. 5, 1973 [21] Appl. No.: 338,093

[52] U.S. Cl. 3/1; 3/DIG. 2; 128/1 D; 417/394; 417/479 [51] Int. Cl.A6lf 1/24 [58] Field of Search.. 3/1, DIG. 2; 128/1 D, DIG. 3, 128/214R, 346; 417/383, 394, 479

[56] References Cited UNITED STATES PATENTS Foley 128/346 PrimaryExaminerRonald L. Frinks Attorney, Agent, or Firm-Frank R. Trifari [5 7ABSTRACT An implantable artificial heart pump or heart assist forproviding or enhancing a controlled cyclic blood flow through an artery,the pump including a tubular section secured between adjacent ends of asevered artery forming a continuous blood flow passage, and having aplurality of axially spaced but adjacent sleeves encircling thissection. The sleeves are sequentially constricted about the tubularsection to provide alternately pumping and suction upon the bloodflowing through the section, the sleeves being energized by high and lowpressure working fluid from an external or implantable power source.Where the power source is an implantable Stirling engine, pressurevariations are available from the gas working space, or from an oil pumpin the crankcase, or from a compressor driven by the engine.

8 Claims, 14 Drawing Figures PATENTEB HAY 2 7 I975 SHEET 1 OF 5 PATENTEDW27 I975 v 3,885 251 SHEET 20? 5 PMENIEW 3885251 SHEET 38F 5 SECTION ISECTION 2 SECTION 3 f L .A M

STAGES 2 I I SUCTION 5 fPUMP T 6 l A J Fig. 7

PRESSURE A SLEEVE HIGH U K 2 [SLEEVE 3 Low-'- TIME +2-+-3+4+5+6'l4PERlODS STAGES l-6 SUCTION W FORCING CYCLE CYCLE Fig.8.

PATEHTEB BIAYZT I975 SHEET u or 5 Fig."

Fig;

PATENTED EAY 27 I975 SHEET 5 BF 5 PERIOD PERIOD 2 PERIOD 3 PERIOD 6PERIOD 5 PERIOD 4 RIOD a PERIOD 6 p PERIOD 5 Hi PERIOD 4 PERIOD 2 PERIOD3 1 ARTIFICIAL HEART PUMP OR ASSIST BACKGROUND OF THE INVENTION Existingartifical heart pumps generally comprise substitute or assist mechanismswhich include one or more valves which are cyclically opened and closed,in response to either the pressure build-up of blood on the valve or toa timing device separate from the valve. In all of the heart pumpshaving valves there are necessarily stagnation points in the blood flowpath; namely a part of the flow channel where a portion of the bloodflow is halted from flowing for a prolonged period of time, and in itsworst case where a portion of the blood flow is permanently halted.Blood in the vicinity of stagnation points has a tendency to coagulate,deposit, or build up on the adjacent valve surfaces, which impedessubsequent flow of blood past said surfaces. Such blood clots mayeventually break loose and cause fatal injury to the patient.

A further problem area in typical heart assist devices utilizing valvesis that some constituents of the blood may be damaged due to excessivepressure, velocity and shear forces occurring when a valve is beingclosed and the pressure drop through the reduced-size flow passage issubstantially increased over normal values.

The new invention is a mechanism for use in a human or animal body toimprove blood flow, the mechanism having structure and geometry whichavoids or at least reduces significantly the above-mentioned problems.

SUMMARY OF THE NEW INVENTION implantable pump in communication with thehigh and low pressure variations occurring, in its preferred embodiment,in a pressure source such as an implantable Stirling or Rankin engine,using the gas working space, or oil pump, or the high and low pressurevariations of a compressor driven by the engine. The new device includesa tubular section that is joined to and between the severed ends of anartery, such that the blood will have a continuous and substantiallyuninterrupted flow path through the artery and the tube-section. Atleast two and preferably three sleeves axially spaced apart butadjacent, encircle this section. Each sleeve has its diameter cyclicallycontracted and enlarged about the tube, such that the bore or flowpassage through the tube is cyclically (a) constricted to reduce or stopblood flow and then (b) enlarged to permit normal flow therethrough.When all three sleeves are subjected to the high pressure, all would beexpanded, and the tube and artery continuous therewith would fill withblood. In operation the first sleeve (which would be designated as inthe upstream position) is constricted; this is followed by the secondsleeve being constricted while the first remains constricted, and thenthe third is constricted while the first and second remain constricted.This tends to force the blood from the first into the secend, then intothe third, and finally out of all of the sleeve areas and downstream.Still later, the two sleeves at the downstream end are kept closed toprevent backflow while the first sleeve is opened such that a new chargeof blood can begin to enter the pump mechanism. Then the second is alsoopened, followed by the third, such that all are open again, thissequence functioning at least in part as a suction stage.

One possible sleeve configuration comprises a tubular member formed intoa ring that has one end sealed and the other end connected to a sourceof fluid that is supplied either at a low or a high relative pressure.The ring has a normal diameter, and application of the high pressurecauses the ring to uncoil and enlarge its diameter; the rings resiliencewill return it to its normal diameter when pressure is reduced ordiscontinued. Alternatively, the sleeves (rings) could be designed tocontract or reduce in diametral dimension upon the application of highfluid pressure, with their resilience returning them to a normalenlarged diameter.

A valve or timing mechanism situated between the source of fluid and thesleeves, will control the selection of sleeves to be pressurized toalter the diameter of each relative to the others. Since these sleevescontact and operate on the outer surface of the tube, they are entirelyexternal of the actual blood flow, which overcomes numerousdisadvantages in prior art devices, as discussed below. Anothervariation of the above invention would be to leave the artery unsevered,to omit the tube section, and position the sleeves directly upon theouter surface of the artery.

The pump mechanism of this invention has a variety of significantadvantages over prior art pumps and heart assists. First, there are nostagnation points for the blood flow throughout the entire mechanism;the mechanism is in fact totally external of the artery, such that theblood flows through a substantially clear and unobstructed tubularportion of the artery that is free of valves or other obstacles found inother pumps. As mentioned above, this stagnation problem has beensignificant, and to avoid it is a considerable benefit and achievement.Second, the pump mechanism is extremely uncomplicated and inexpensive,in comprising simple sleeves which change dimension but otherwise do notmove and do not have to mate with other parts, and do not have closetolerances, and do not have seals, bearings, and. other parts which canwear out. The sleeves will merely expand and constrict, and there arenumerous materials available including metals, plastics and rubber whichhave proven ability to flex thousands or millions of cycles withoutdeteriorating excessively or losing their necessary characteristics.Also, the sleeves would be secured together in some manner to maintaintheir axial spacing, such that the constriction of one sleeve effectingthe blood flow therein would not be remote and unrelated to theapplication of pressure upon blood in the adjacent sections of theartery. The number of sleeves can be increased to provide a smootherflow of the blood, however a minimum number of two sleeves is required,and presumably three would function reasonably well.

In order to operate a pump of this type, it is necessary to have asource of both high and low pressure gas or liquid working fluid. Animplantable Stirling engine has a gas working space and also alubricating oil pump that experience such appropriate high and lowpressure differentials; this gas space or the oil pump can be connecteddirectly to the sleeves through a valve which automatically selects thesuitable pressure level for each sleeve. Alternatively a Stirling orother implantable power source can drive a compressor whose high and lowpressure ducts are fed to the sleeves via a valve. Stirling engines canoperate over a long, extended period of time, by using an isotope heatsource, and can run maintenance-and-adjustment-free. The sleeves couldbe timed to operate at the same rate as the compressor and/or theengine, or could cycle at a multiple or fraction of the valve speed.

A preferred embodiment of this invention is disclosed with reference tothe drawings described below.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic diagram of heartassist system including an artery pump and a Stirling engine providinghigh and low working gas pressure.

FIG. 2 is schematic diagram of another embodiment of a system similar toFIG. 1, wherein a Stirling engine drives a compressor which provides thehigh and low pressures.

FIG. 3 is a schematic diagram of another embodiment similar to FIGS. 1and 2, with the oil pump in the crankcase providing high and lowpressures.

FIG. 4 is a partial elevation view of the pump of the new invention.

FIG. 5 is a sectional view taken along line 55 of FIG. 4.

FIG. 6 is a sectional view taken along line 66 of FIG. 4.

FIG. 7 is a schematic view showing the pumping and suction cycles of thedevice of FIG. 4.

FIG. 8 is a pressure vs time diagram showing six periods for a complete(FIG. 7) cycle of the FIG. 4 embodiment.

FIG. 9 is a partial elevation view in section of a second embodiment ofthe invention with a center core.

FIG. 10 is a sectional view of another embodiment similar to FIG. 9.

FIG. 11 is an end view taken along line 1I11 in FIG. 10.

FIG. 12 is a sectional view taken along line 12-12 in FIG. 10.

FIG. 13 is a diagrammatic view of a rotary control valve to selectivelyprovide high and low pressure to the three sleeves in selective sequenceof the device in FIGS. 4, 9 and 10.

- DESCRIPTION OF THE PREFERRED EMBODIMENT The invention as a wholeimplantable system is shown in FIG. 1 where a Stirling engine 1 has aworking or compression space that experiences high and low pressuresavailable at ports 2 and 3 respectively, which are connected via ductsand corresponding high and low pressure buffer tanks h and h; to a valve4; one embodiment of this valve is shown in detail in FIG. 13. The valveselectively feeds high and low pressure to sleeves 5, 6, and 7 whichencircle tube 8 connected between the severed ends 9 and 9' of an arteryas a continuous blood flow duct, the valve being controlled by aconnection 4 with engine. The sleeves and tube 8 together form the pumpcomponent 10 which pumps blood in the direction of the arrows. theoperation of the pump and valve components will be described in detailbelow, while the operation of a Stirling engine is known and describedin numerous publications such as US. Pat. Nos. 3,443,079, 2,885,855,3,318,089 and 3,318,100.

FIG. 2 shows schematically a variation from FIG. 1 with similarcomponents given the same reference numerals but modified, for example,from 1 to la. Accordingly a Stirling engine 1a has a mechanical orhydraulic power output 1b that drives compressor 1c which has a lowpressure connection 3a feeding a buffer tank 3b to valve 4a, and a highpressure connection 2a which also feeds valve 4a via a buffer tank 1dfor storing high pressure working fluid. The valve 4a automaticallyfeeds the appropriate high and low pressure fluid to sleeves 5a, 6a and7a about tube 8a of pump 10a.

FIG. 3 shows a third variation wherein the heart assist system comprisesthe lubricating oil pump la in the crankcase 1f of Stirling engine lg.High pressure oil is fed to a high pressure buffer tank 3c and then tothe control valve 4b for sleeves 5b, 6b. and 7b. A spring bellowsexpander may be situated inside of the buffer tank (see FIG. 3a) willhelp maintain a generally constant tank pressure when valve 4a opens anddraws vfluid from the tank. The spring-loaded or gas-pressure biasedbellows in the tank would maintain an oil supply pressure substantiallyconstant. Where a Stirling engine is utilized to provide directly, orindirectly the high and low pressure fluid, a radioactive isotopecapsule is suggested to supply heat for long-term operation of theengine.

The pump 10 of FIG. 1 is shown in FIG. 4- where a section of tubing issurrounded by three sleeves l1, l2 and 13. The direction of flow is fromleft to right as indicated by arrow 14, and the tube has a nominalundisturbed diameter d as compared to a constricted diameter d resultingfrom reducing the diameter of the sleeves. FIG. 5 shows the tube 10c andsleeve 11 in an expanded state, and FIG. 6 shows the tube and sleeve 13or 12 in a contracted state. Each sleeve is normally constricted as inFIG. 6 and is expanded when a fluid pressure is applied to the internalchamber of the hollow sleeve causing it to expand as indicated in FIG.5.

The operation of the above pumping device is shown in six stagessymbolically in FIG. 7 and diagrammatically in FIG. 8. In stage 1 ofFIG. 7 the first sleeve is expanded while the second and third sleevesare constricted; this corresponds to the chart of FIG. 8 which showssleeve 1 at high pressure, namelythat it is expanded and blood can fillthe space it encloses, in contrast to sleeves 2 and 3 which areindicated to be energized with low fluid pressure or that they areconstricted resulting in greater resistance to the blood flow. Stage 2of FIG. 7 shows that the first two sleeves are expanded while the thirdremains constricted; FIG. 8 in stage 2, corresponds by showing sleeves land 2 energized with high fluid pressure while sleeve 3 is still at lowpressure. Stage 3 in FIG. 6 shows all three sections to be expanded suchthat all three sleeves are being energized with high pressure fluid, andthis corresponds to FIG. 8 stage 3 where all three sleeves are indicatedto be at high pressure. Stage 4 in FIG. 7 shows the first section to beconstricted by corresponding action of sleeve 1; FIG. 8 shows thecorresponding diagram whereby only sleeve 1 is constricted, whereassleeves 2 and 3 remain expanded, that is, subjected to high energizingfluid pressure. Stage 5 shows that the first sleeve has remainedconstricted and the second is constricted thus forcing net flow in thedirection of the arrow to the right out through section 3. And, stage 6shows all sleeves to be constricted thus forcing the net flow fromsection 3 further outward, while the first two closed sections preventto some extent the fluid from moving backward. As the cycle beingsagain, we return to stage 1 where section 1 is opened while sections 2and 3 remain closed. This permits fluid to enter section 1 while itsubstantially prevents fluid from flowing backwards into sections 2 and3. Next, section 2 is opened which allows more net fluid flow to move tothe right into the pump and in fact draws the fluid in becauseresilience of the section causes it to open creating a partial vacuumtherein. And, finally, all three sections are opened 'in stage 3. Againin stage 4 the first section is closed which forces net fluid flowtoward the right in the direction of the arrows in FIG. 7.

FIGS. 7 and 8 demonstrate a pumping action comprising a suction orpriming cycle in stages 1, 2 and 3, and a pumping forcing cycle instages 4, 5, and 6. It would be possible to use only two sleeves but theefficiency of the pump would be considerably reduced.

FIG. 9 shows another embodiment of the invention which is similar to butmodified from that in FIG. 4. The pumping device is in a housing 16 witha section of tubing 17 axially disposed in a housing. The entire pumpingdevice is to be attached to the severed ends l8, 19 of an artery alongjunction lines 18 and 19'. The three sleeves for producing the pumpingaction are shown as 20, 21 and 22 with each being connected to a fluidport 20, 21' and 22' which feeds energizing fluid under pressure to thesleeves for expanding same according to the method earlier described.

Significantly different in the FIG. 9 embodiment from FIG. 4, is centercore 23 which is fixedly positioned in the center or thereabouts of thetube section 17; FIG. 11 shows streamlined webs 29 at the entrance andexit of the tube for supporting the core element. Sleeve 20 as shownconstricts the flexible tube 17, until it closes substantially orcompletely about core 23; subsequent closing of sleeve 21 would forcefluid flow in the direction to the right, past sleeve 22. It should beobvious that the presence of the core allows the constricted tube tonearly completely close off flow in contrast to the prior embodimentwhere there is no core and the constriction of the first sleeve wouldonly tend to restrict flow, but obviously there would be considerableleakage backward because the passage within the tube remains open. It iscontemplated that this pump device of FIG. 9 would be embedded as a unitwithin the body while the two ends thereof are attached to the severedartery at 19 and 18, and the fluid ports 20', 21' and 22' would beattached to pressurized fluid means to be discussed later.

FIG. 10 shows a more detailed view of an embodiment similar to that ofFIG. 9. The sleeves 24, 25 and 26 are indicated as coil sections ofhollow tubing each connected to a port through which pressurized fluidis directed. It is necessary to support the center core 27 centrally oftubing 28, and this is done by webs 29 shown in FIG. 11 which is a rightend view of FIG. 10. The webs are thin and streamlined and representminimum obstruction to the flow of blood in the annular space 29 aboutthe center core and within tube section 28. FIG. 12 includes a sectionalview of the port 30 for energizing a sleeve 24.

With any of the above-described pump components it is necessary toprovide both high and low pressure fluid to the different sleeves in aproper sequence. This may be accomplished with a compressor or othermeans to develop high and low pressure in a liquid or a gas, and a valvesuch as rotary valve'means according to FIG. 13 which directs fluidflow' to appropriate sleeves. This valve has outlets P,, P P connectedrespectively to sleeves 24, 25, and 26 of FIG. 10, or to three sleevesof any other embodiment; it also has a low pressure inlet P and a highpressure inlet P During stage 1 for example, with FIG. 10, we will needa high pressure at sleeve 24 and low pressure at sleeves 25 and 26. Theinner rotor permits communication of high pressure inlet P with outlet Pand low pressure inlet P with outlets P and P The exit ports arepositioned around the housing of the valve such that rotation of therotor exposes appropriate exit ports at the correct timing to provide acyclic pressure variation for'the three sleeves, or any number that ischosen, according to FIGS. 7 and 8.

It should .be noted that the section of tubing i.e. 17 in FIG. 9, usedin any of the pumps, preferably should have resiliency, such that ittends to hold its open shape; this eliminates direct outward radialpulling contact between the sleeve and section of the tube. Furthermore,each sleeve is resilient member which tends to hold its constrictedshape at low energizing pressure. Thus, when a sleeve is energized byhaving a pressure applied to its hollow inner chamber, and said sleeveexpands, the portion of the tube adjacent to the sleeve will expand onits own due to its own resiliency. Obviously, it would be possible toreverse these features such that the sleeve would have a normal expandedcondition and that the application of fluid pressure would cause it tocontract; then the tubular section within the sleeveswould also have anormal open position with its resilience tending to maintain it thatway; when pressure to ,the sleeve was reduced or relaxed, the sleeve andtube therein would automatically open to full diameter.

The opening of- 'the first and second sections of the tube while thethird section remains closed, acts as a suction or priming" phase of thedevice. as the sleeve creates a greater volume and a partial vacuum suchthat blood will flow into these open sections mainly in the pumpingdirection; and during later phases of the cycle the blood will be pumpedout mainly in the same direction.

If a gas rather than a liquid, is used to pressurize the sleeves, thendry friction seals (made from a plastic sold under the trademark Rulon)might be necessary in the valve mechanism. However, ifa liquid such asoil is used as the energizing fluid, then the sealing requirements aregreatly; reduced, and metal surfaces moving in close proximity couldfulfill the scaling function satisfactorily. The valve shown in FIG. 13can be designed to control the flow to as many sleeves as desired,except that the diameter .of the valve would increase as the number offlow connections increased. In general, if the pump has N number ofsleeves, then it would have to have N7number of flow outlets, and theangle 6 in the valve according to FIG. 13 would be 1r/N radians. Whenone or more sleeves constrict the central tube, wrinkles in theconstricted portion can be avoided by axially fixing the opposite endsof the tube", then the constricted part of the tube is also stretchedlengthwise, and Jwill not experience compression on bending.

The structures shown in these drawings are merely preferred embodimentsfor practising the invention, these structures being merelyrepresentative of the invention with no intention that the scope of theinvention be limited to their configurations.

What is claimed is:

1. An implantable heart pump for pumping and controlling the flow ofblood through an artery which is severable to expose two adjacent endsto accommodate the pump therebetween, this pump being operable withfirst and second sources of high and low pressure fluid respectively,the pump comprising a tube securable between said severed ends of saidartery to form a continuous blood flow passage, at least two sleeveseach having a generally cylindrical bore at least partially surroundingand contacting said tube, the sleeves being axially spaced apart butadjacent to each other, a core element formed as a rod fixedlypositioned generally centrally within the bore of said tube and adjacentthe inner surface thereof, the tube having a bore diameter that isvariable between large and small, each sleeve being responsive to apressure change whereby its diameter is variable between large and smallcorresponding to said tube bore diameters, and valve means forcommunicating selectively said high and low pressure sources to saidsleeves, whereby each sleeve periodically has a. a small diameter forconstricting the tube to have a small bore diameter at the area of thetube adjacent said sleeve, and

b. a large diameter permitting a corresponding large bore diameter ofsaid tube with the tubes inner surface at that area being urged closelyagainst said core to prevent blood flow in that area, the valveproviding a predetermined sequence of constrictions and expansions ofthe sleeves and therefor of the tube to produce a pumping action in onedirection on the blood flow therein, said apparatus further comprisingan implantable Stirling engine including a heat source for operating theengine, the engine having a working space wherein working gasexperiences a cyclic pressure variation between high and low, theapparatus further comprising duct means communicating said high and lowpressure gas to said valve means.

2. An implantable heart pump for pumping and controlling the flow ofblood through an artery which is severable to expose two adjacent endsto accomodate the pump therebetween, this pump being operable with firstand second sources of high and low pressure fluid respectively, the pumpcomprising a tube securable between said severed ends of said artery toform a continuous blood flow passage, at least two sleeves each at leastpartially surrounding said tube, the sleeves being axiallysp'aced apartbut adjacent to each other, the tube having a bore diameter that isvariable between large and small, each sleeve being responsive to apressure change whereby its diameter is variable between large and smallcorresponding to said tube bore diameters, valve means forcommunicating"selectively said high and low pressure sources to saidsleeves, whereby each sleeve periodically has a small diameter forconstricting the tube to have a small bore diameter adjacent saidsleeve, and a large diameter permitting a corresponding large borediameter of said tube, the valve providing a predetermined sequence ofconstrictions and expansions of the sleeves and therefore of the tube toproduce a pumping action in one direction on the blood flow therein, thepump further comprising an implantable Stirling engine including a heatsource for'roperatingthe engine and a lubricating oil pump inthecrankcase of the engine for providing oil underpressure, with crankcaseinterior being at a pressure lower .than-said oil pump pressure, theapparatus further comprising means communicating a portion of said oil'under pressure to said valve means as said source of high pressurefluid, and means communicating the crankcase. interior to said valvemeans as said source of low pressure fluid. 3. An implantable heart pumpfor pumping and controlling the flow of blood through an artery which isseverable to expose two adjacent ends to accommodate the pumptherebetween, this pump being operable with first and second sources ofhigh and low pressure fluid respectively, the pump comprising animplantable Stirling engine including a heat source for operating theengine and a mechanical power output of the engine a compressor drivenby said power output, the compressor having a high pressure output portand a low pressure inlet port which constitute said high and lowpressure sources of fluid, duct means communicating said ports to avalve means, and corresponding high and low pressure buffer chambersrespectively intermediate said valve and said ports, a tube securablebetween said severed ends of said artery to form a continuous blood flowpassage, at least two sleeves each at least partially surrounding saidtube, the sleeves being axially spaced apart but adjacent to each other,the tube having a bore diameter that is variable between large andsmall, each sleeve being responsive to a pressure change whereby itsdiameter is variable between large and small corresponding to said tubebore diameters, said valve means for communicating selectively saidhighand low pressure sources to said sleeves, whereby each sleeveperiodically has V a. a small diameter for constricting the tube to havea small bore diameter adjacent said sleeve, and b. a large diameterpermitting a corresponding large bore diameter of said tube, the valveproviding a predetermined sequence of constrictions and expansions ofthe sleeves and therefor of the tube to produce a pumping action in onedirection on the blood flow therein.

4. An implantable heart pump for pumping and controlling the flow ofblood through an artery which is severable to expose two adjacent endsto accommodate the pump therebetween, this pump being operable withfirst and second sources of high and low pressure fluid respectively,the pump comprising a tube securable between said severed ends of saidartery to form a continuous blood flow passage, at least two sleeveseach at least partially surrounding said tube, the sleeves being axiallyspaced apart but adjacent to each other, the tube having a bore diameterthat is variable between large and small, each sleeve being responsiveto a presthat is expandable to a large diameter when high pressure fluidis communicated to said inlet-outlet port, each ring having resilienceto return to its normal small diameter when. in communication with lowpressure fluid whereby each sleeve periodically has a small diameterforconstricting the tube to have a small bore diameter'adjacent saidsleeve, and a large diameter permittingga corresponding large borediameter of said tube, the valve providing a predetermined sequence ofconstrictions and expansions of the sleeves and therefor of the tube toproduce a pumping action in one direction on the blood flow therein.

5. An implantable heart pump for pumping and controlling the flow ofblood through an artery which is severable to expose two adjacent endsto accommodate the pump therebetween, this pump being operable withfirst and second sources of high and low pressure fluid respectively,the pump comprising a tube securable between said severed ends of saidartery to form a continuous blood flow passage, a core element formed asa rod fixedly positioned generally centrally within the bore of saidtube and adjacent the inner surface thereof, at least two sleeves eachat least partially surrounding said tube, the sleeves being axiallyspaced apart but adjacent to each other, the tube having a bore diameterthat is variable between large and small, each sleeve being responsiveto a pressure change whereby its diameter is variable between large andsmall corresponding to said tube bore diameter, valve means forcommunicating selectively said high and low pressure sources to saidsleeves, the pump further comprising an implantable Stirling engineincluding a heat source for operating the engine, the engine having aworking space wherein working gas experiences a cyclic pressurevariation between high and low, the apparatus further comprising ductmeans communicating said high and low pressure gas to said valve meanswhereby each sleeve periodically has a small. diameter for constrictingthe tube to have a small bore diameter adjacent said sleeve, and a largediameter permitting a corresponding large bore diameter of said tube,and constriction of each sleeve constricts the adjacent part of saidtube, with the inner surface of said part urged closely against saidcore to prevent blood flow past said part, the valve providing apredetermined sequence of constrictions and expansions of the sleevesand therefor of the tube to produce a pumping action in one direction onthe blood flow therein.

6. Apparatus according to claim wherein said sleeves define an axiallength between them and said core has length approximately equal to saidaxial length, the apparatus further comprising web means for fixedlypositioning each end of said core relative to said tube.

7. A heart pump for attachment between the severed ends of a severedartery, comprising an implantable Stirling engine including a fluidtherein that is cyclically under high and low pressure, a tube securablebetween said severed ends to form a continuous blood flow path, threesleeves axially spaced and having generally cylindrical bores positionedabout and in contact with said tube, a core element formed as a rodfixedly positioned generally centrally within the bore of said tube andadjacent the inner surface thereof, valve means for cyclically andsequentially communicating said high and low pressure fluid to saidsleeves, a buffer tank between said valve and each of said high and lowpressure sources, means interconnecting said engine and said valve forcyclically controlling said valve according to the operation cycle ofthe engine, said sleeves designated first, second and third movingdownstream of the flow, each having its diameter reduced when said highpressure is communicated thereto and expanded when said low pressure iscommunicated thereto and the tube in the areas surrounded by the sleeveshaving corresponding diameter constrictions and expansions with thetubes inner surface at each of said areas being urged closely againstsaid core to prevent blood flow in said areas respectively, whereby thetube diameter adjacent the sleeves is as follows:

First Second Third 1. Stage large small small 2. do. large large small3. do. large large large 4. do. small large large 5. do. small smalllarge 6. do, small small small.

uous blood flow passage, at least two sleeves each hav-' ing a generallycylindrical bore at least partially surrounding and contacting saidtube, the sleeves being axially spaced apart but adjacent to each other,a core element formed as a rod fixedly positioned generally centrallywithin the bore of said tube and adjacent the inner surface thereof, thetube having a bore diameter that is variable between large and small,each sleeve being responsive to a pressure change whereby its diameteris variable between large and small corresponding to said tube borediameters, and valve means for communicating selectively said high andlow pressure sources to said sleeves, whereby each sleeve periodicallyhas a. a small diameter for constricting the tube to have a small borediameter at the area of the tube adjacent said sleeve with the tubes sinner surface at the area being urged closely against said core toprevent blood flow in that area, and b. a large diameter permitting acorresponding large bore diameter of said tube, and thereby permittingblood flow, the valve providing a predetermined sequence ofconstrictions and expansions of the sleeves and therefor of the tube toproduce a pumping action in one direction on the blood flow therein.

1. An implantable heart pump for pumping and controlling the flow ofblood through an artery which is severable to expose two adjacent endsto accommodate the pump therebetween, this pump being operable withfirst and second sources of high and low pressure fluid respectively,the pump comprising a tube securable between said severed ends of saidartery to form a continuous blood flow passage, at least two sleeveseach having a generally cylindrical bore at least partially surroundingand contacting said tube, the sleeves being axially spaced apart butadjacent to each other, a core element formed as a rod fixedlypositioned generally centrally within the bore of said tube and adjacentthe inner surface thereof, the tube having a bore diameter that isvariable between large and small, each sleeve being responsive to apressure change whereby its diameter is variable between large and smallcorresponding to said tube bore diameters, and valve means forcommunicating selectively said high and low pressure sources to saidsleeves, whereby each sleeve periodically has a. a small diameter forconstricting the tube to have a small bore diameter at the area of thetube adjacent said sleeve, and b. a large diameter permitting acorresponding large bore diameter of said tube with the tubes innersurface at that area being urged closely against said core to preventblood flow in that area, the valve providing a predetermined sequence ofconstrictions and expansions of the sleeves and therefor of the tube toproduce a pumping action in one direction on the blood flow therein,said apparatus further comprising an implantable Stirling engineincluding a heat Source for operating the engine, the engine having aworking space wherein working gas experiences a cyclic pressurevariation between high and low, the apparatus further comprising ductmeans communicating said high and low pressure gas to said valve means.2. An implantable heart pump for pumping and controlling the flow ofblood through an artery which is severable to expose two adjacent endsto accomodate the pump therebetween, this pump being operable with firstand second sources of high and low pressure fluid respectively, the pumpcomprising a tube securable between said severed ends of said artery toform a continuous blood flow passage, at least two sleeves each at leastpartially surrounding said tube, the sleeves being axially spaced apartbut adjacent to each other, the tube having a bore diameter that isvariable between large and small, each sleeve being responsive to apressure change whereby its diameter is variable between large and smallcorresponding to said tube bore diameters, valve means for communicatingselectively said high and low pressure sources to said sleeves, wherebyeach sleeve periodically has a small diameter for constricting the tubeto have a small bore diameter adjacent said sleeve, and a large diameterpermitting a corresponding large bore diameter of said tube, the valveproviding a predetermined sequence of constrictions and expansions ofthe sleeves and therefore of the tube to produce a pumping action in onedirection on the blood flow therein, the pump further comprising animplantable Stirling engine including a heat source for operating theengine and a lubricating oil pump in the crankcase of the engine forproviding oil under pressure, with crankcase interior being at apressure lower than said oil pump pressure, the apparatus furthercomprising means communicating a portion of said oil under pressure tosaid valve means as said source of high pressure fluid, and meanscommunicating the crankcase interior to said valve means as said sourceof low pressure fluid.
 3. An implantable heart pump for pumping andcontrolling the flow of blood through an artery which is severable toexpose two adjacent ends to accommodate the pump therebetween, this pumpbeing operable with first and second sources of high and low pressurefluid respectively, the pump comprising an implantable Stirling engineincluding a heat source for operating the engine and a mechanical poweroutput of the engine a compressor driven by said power output, thecompressor having a high pressure output port and a low pressure inletport which constitute said high and low pressure sources of fluid, ductmeans communicating said ports to a valve means, and corresponding highand low pressure buffer chambers respectively intermediate said valveand said ports, a tube securable between said severed ends of saidartery to form a continuous blood flow passage, at least two sleeveseach at least partially surrounding said tube, the sleeves being axiallyspaced apart but adjacent to each other, the tube having a bore diameterthat is variable between large and small, each sleeve being responsiveto a pressure change whereby its diameter is variable between large andsmall corresponding to said tube bore diameters, said valve means forcommunicating selectively said high and low pressure sources to saidsleeves, whereby each sleeve periodically has a. a small diameter forconstricting the tube to have a small bore diameter adjacent saidsleeve, and b. a large diameter permitting a corresponding large borediameter of said tube, the valve providing a predetermined sequence ofconstrictions and expansions of the sleeves and therefor of the tube toproduce a pumping action in one direction on the blood flow therein. 4.An implantable heart pump for pumping and controlling the flow of bloodthrough an artery which is severable to expose two adjacent ends toaccommodate the pump therebetween, this pump being operable with firstand second sources of high and lOw pressure fluid respectively, the pumpcomprising a tube securable between said severed ends of said artery toform a continuous blood flow passage, at least two sleeves each at leastpartially surrounding said tube, the sleeves being axially spaced apartbut adjacent to each other, the tube having a bore diameter that isvariable between large and small, each sleeve being responsive to apressure change whereby its diameter is variable between large and smallcorresponding to said tube bore diameters, valve means for communicatingselectively said high and low pressure sources to said sleeves, andwherein each sleeve comprises a tubular element defining a ringshapedhollow chamber with only one inlet-outlet port, each ring having anormal small diameter that is expandable to a large diameter when highpressure fluid is communicated to said inlet-outlet port, each ringhaving resilience to return to its normal small diameter when incommunication with low pressure fluid whereby each sleeve periodicallyhas a small diameter for constricting the tube to have a small borediameter adjacent said sleeve, and a large diameter permitting acorresponding large bore diameter of said tube, the valve providing apredetermined sequence of constrictions and expansions of the sleevesand therefor of the tube to produce a pumping action in one direction onthe blood flow therein.
 5. An implantable heart pump for pumping andcontrolling the flow of blood through an artery which is severable toexpose two adjacent ends to accommodate the pump therebetween, this pumpbeing operable with first and second sources of high and low pressurefluid respectively, the pump comprising a tube securable between saidsevered ends of said artery to form a continuous blood flow passage, acore element formed as a rod fixedly positioned generally centrallywithin the bore of said tube and adjacent the inner surface thereof, atleast two sleeves each at least partially surrounding said tube, thesleeves being axially spaced apart but adjacent to each other, the tubehaving a bore diameter that is variable between large and small, eachsleeve being responsive to a pressure change whereby its diameter isvariable between large and small corresponding to said tube borediameter, valve means for communicating selectively said high and lowpressure sources to said sleeves, the pump further comprising animplantable Stirling engine including a heat source for operating theengine, the engine having a working space wherein working gasexperiences a cyclic pressure variation between high and low, theapparatus further comprising duct means communicating said high and lowpressure gas to said valve means whereby each sleeve periodically has asmall diameter for constricting the tube to have a small bore diameteradjacent said sleeve, and a large diameter permitting a correspondinglarge bore diameter of said tube, and constriction of each sleeveconstricts the adjacent part of said tube, with the inner surface ofsaid part urged closely against said core to prevent blood flow pastsaid part, the valve providing a predetermined sequence of constrictionsand expansions of the sleeves and therefor of the tube to produce apumping action in one direction on the blood flow therein.
 6. Apparatusaccording to claim 5 wherein said sleeves define an axial length betweenthem and said core has length approximately equal to said axial length,the apparatus further comprising web means for fixedly positioning eachend of said core relative to said tube.
 7. A heart pump for attachmentbetween the severed ends of a severed artery, comprising an implantableStirling engine including a fluid therein that is cyclically under highand low pressure, a tube securable between said severed ends to form acontinuous blood flow path, three sleeves axially spaced and havinggenerally cylindrical bores positioned about and in contact with saidtube, a core element formed as a rod fixedly positioned generallycentrally within the bore of said tube and adjacent the inner surfacethereof, valve means for cyclically and sequentially communicating saidhigh and low pressure fluid to said sleeves, a buffer tank between saidvalve and each of said high and low pressure sources, meansinterconnecting said engine and said valve for cyclically controllingsaid valve according to the operation cycle of the engine, said sleevesdesignated first, second and third moving downstream of the flow, eachhaving its diameter reduced when said high pressure is communicatedthereto and expanded when said low pressure is communicated thereto andthe tube in the areas surrounded by the sleeves having correspondingdiameter constrictions and expansions with the tubes inner surface ateach of said areas being urged closely against said core to preventblood flow in said areas respectively, whereby the tube diameteradjacent the sleeves is as follows:
 8. An implantable heart pump forpumping and controlling the flow of blood through an artery which isseverable to expose two adjacent ends to accommodate the pumptherebetween, this pump being operable with first and second sources ofhigh and low pressure fluid respectively, the pump comprising a tubesecurable between said severed ends of said artery to form a continuousblood flow passage, at least two sleeves each having a generallycylindrical bore at least partially surrounding and contacting saidtube, the sleeves being axially spaced apart but adjacent to each other,a core element formed as a rod fixedly positioned generally centrallywithin the bore of said tube and adjacent the inner surface thereof, thetube having a bore diameter that is variable between large and small,each sleeve being responsive to a pressure change whereby its diameteris variable between large and small corresponding to said tube borediameters, and valve means for communicating selectively said high andlow pressure sources to said sleeves, whereby each sleeve periodicallyhas a. a small diameter for constricting the tube to have a small borediameter at the area of the tube adjacent said sleeve with the tubes''sinner surface at the area being urged closely against said core toprevent blood flow in that area, and b. a large diameter permitting acorresponding large bore diameter of said tube, and thereby permittingblood flow, the valve providing a predetermined sequence ofconstrictions and expansions of the sleeves and therefor of the tube toproduce a pumping action in one direction on the blood flow therein.